One-shot pre-equalization scheme based on frequency pilot tones for bandwidth-limited IM/DD DCI transmission.

Abstract

O-band intensity modulation and direct detection (IM/DD) transmission offers a promising solution for high-speed data center interconnects (DCIs). Additionally, the introduction of bismuth-doped fiber amplifiers (BDFAs) results in less nonlinear impact and a higher link budget compared with semiconductor optical amplifiers (SOAs). However, with these key issues resolved, the system bandwidth limitation emerges as the next critical bottleneck for high-speed O-band DCI transmission that limits overall performance. In this letter, we propose an efficient pre-equalization (pre-Eq) method based on the frequency pilot tones (FPTs), utilizing detectors for both magnitude and phase responses. With a single-shot characterization, the FPT-based pre-Eq method can effectively compensate for high-frequency fading caused by bandwidth limitation. We successfully demonstrate the O-band transmission of a 100-GBaud PAM-4 signal over 40-km standard single-mode fiber (SSMF) under a 10-dB bandwidth limitation of around 30 GHz. Our results show that the FPT-based pre-Eq significantly outperforms the constant modulus algorithm (CMA)-based pre-Eq.